Regulating system



25"? 1947. H, Q JENKS 2,420,881

REGULATING SYSTEM v Filed Sept. 20, 1944 Haro/d C. Jenk.

Pnemed Mey zo, 1941 UNITED STATESv PATENT orifice REGULATING SYSTEMHarold C. Jenks, Cincinnati, Ohio, assigner to Westinghouse ElectricCorporation, East Pittsburgli, Pa., a corporation PennsylvaniaApplication september 2o, 1944, sei-iai No. 554,911 y s chime. (ci.17a-24s);

This invention relates to electrical systems and in particular to powerfactor regulating systems.

An object of this invention is to provide a regulating system responsiveto fluctuations in power factor to maintain the power factor of a loadsystem at substantially a predetermined value under no-load and loadconditions.

Another object of this invention is to regulate the power factor of a.synchronous motor by utilizing a saturable reactor for controlling theexcitation thereof, the saturation of the reactor being controlled inresponse to the power factor drawn by the synchronous motor.

Otherobjects of this invention will become apparent from the followingdescription when taken in conjunction with the accompanying drawing, thesingle iigure of which is a diagrammatic view of the apparatus andcircuits embodying the teachings of this invention.

Referring to the drawing, a synchronous motor i8 is illustrated ashaving its armature windings I2 connected by conductors I4, I6 and I8through a three-pole switch 20 to load conductors 22,v 24 and 28. Thesynchronous motor i8 is provided with field windings 28 'which areconnected through a rectifying bridge circuit 38, transform` er 82 andsaturable reactor 84 to the load conductors 22 and 24.

The saturable reactor 34 comprises the threelegged core member 38 havingalternating current windings 38- and 48 carried on the outer legsthereof and two opposed direct-current windings 42 and 44 carried by thecenter leg thereof. The alternating current windings 38 and 48 areconnected in series withy the primary windings of transformer 32therebetween and are disposed to be connected by conductors 48 and 48 tothe conductors 22 and 24, respectively. By connecting thealternating-'current windings 38 and 48 in this manner, all the iiux owsin the outer legs of the core member 86 Without passing through thecenter leg when the direct-current windings 42 and 44 are deenergizedand consequently the alternating-current windings with the large amountof iron offer a high impedance to the load current of the reactor andlittle current flows through the primary windings of transformer 82.

The direct-current windings 42 of the reactor 84 are connected to beenergized all the time that the alternating-current windings 38 and 48are energized. Thus the windings 42 are con- 2 j nected through thetransformer 54 across conductors 48 and 48. By connecting thedirectcurrent windings 42 in this manner, a nux will be created thattends to saturate the ironcore member 88 decreasing the impedance ofthealternating-current windings 88 and 48 to the alternating current sothat more current flows through the primary windings of the transformer82. By adjusting resistor -58 and a resistor 58 vconnected in the fieldcircuit of the motor i 0, the

maximum value of excitation for the motor I0 can be determined forestablishing the maximum permissible leading power factor to -be drawnby the motor.

The other direct-current 'windings 44 of the reactor 84 are wound on the,center leg of the `core member 88 in opposition to the direct-cur- I4and I8 is utilized. The transformer 58 is provided with a plurality ofsecondary windings 62, 64, 68, 88 and 18, the purpose of which will benected through an adjustable resistor 50 across the output terminals ofa rectifying bridge circuit 52, the input terminals of which are con- 82of electric valve 12.

explained more fully hereinafter.

In order to control the flow of current in the direct-current windings,the windings 44 are disposed to be connected through an electric valvedischarge device 12 to the secondary windings 68 of the transformer 58.The electric valve 12 comprises an anode 14, a screen grid 18. abiasinggrid 18, a heater 88 and a .cathode 82. The electric valve 12 hasthe characteristics that when used on alternating current voltage, ifrendered conducting by a grid impulse, it will conduct current for theremaining portion of the positive half cycle of the voltage wave butwill be rendered non-conducting when the voltage decreases to the arcdrop value of the valve and will not be reestablished during thenegative half cycle of that voltage wave.

As illustrated, the secondary windings 68. of the transformer 58 forsupplying current to the windings 44 have one of their terminalsconnected by conductor 84 to a terminal of the direct-current-windings44, the other terminal of which is connected by conductor 85 'through anadjustable resistor 88, switch 98 and conductor 82 to the anode 14 ofthe valve 12. The other terminal of the secondary windings 88 isconnected by conductors 84 and 88'to the cathode The resistor 88 isineluded in the circuit just described in order to provide an adjustmentfor determining or limiting the maximum current flow in the windings 44to determine the maximum energization of the windings 44 in oppositionto that of the windings 42, 1,

In order to provide a negative bias of the grid 18 of electric valve 12,the secondary windings 10 of the transformer 58 are connected across theinput terminals of a rectifying bridge circuit 98, one of the outputterminals of which -is connected through the secondary windings of animpulse transformer |02 and a resistor |04 t0 the grid 18, the otheroutput terminal of the bridge circuit being connected by conductor |06through a part of a resistor |08 and conductors |l0, 84 and 86 to thecathode 82,

The impulse transformer |02 is provided for controlling the firing ofthe valve 12 in response to the phase angle of the load system. Asillustrated, the primary windings ||2 of the transformer |02 areconnected to a current transformer ||4 which is disposed in inductiverelation with the load conductor 24. The impulse transformer |02 is of atype well known to industry, the leg of the magnetic core upon which thesecondary windings |00 are wound being so designed that it will saturateVery early in the current cycle and as a result of the rapid saturationwill provide a peaked impulse of considerable magnitude. Thus, althoughthe valve 12 is normally maintained nonconducting bythe negative biasapplied thereto when the impulse transformer |02 impresses its peakedvoltage on the grid biasing circuit, the grid 18 is rendered lessnegative or more positive to cut the critical grid voltage of the valve12 and render the valve conductive.

The phase position 0f the impulse impressed on the grid circuit by theimpulse transformer |02 will be dependent upon the angle of the ycurrentbeing drawn by the synchronous motor. Thus at unity power factor theimpulse comes at the peak of the positive half cycle of the voltage wavewhereas for a leading power factor the impulse comes at an earlier timein the positive half cycle of the voltage wave and for a lagging powerfactor the impulse comes later in the positive half cycle of the voltagewave. Thus with the windings 44 connected across the anode 14 and thecathode 82 of electric valve 12, it is apparent that the current fiowthrough the windings 44 is dependent upon the firing of the valve 12,the conductivity of which is controlled through the impulse transformer|02 in response to the power factor of the system.

As will be apparent if the synchronous motor l0 is pulling a leadingpower factor load as it would be if switch 2D were in the closed circuitposition and switch 90 were in the open circuit position and resistors50 and 56 were properly adjusted, then by closing switch S0 to connectthe regulating system in circuit with the windings 44 of reactor 34, itwill be seen that by reason of the impulse transformer |02 the valve 12will fire early in the positive half cycle of the voltage wave to passcurrent through the directs By thus energizing the current windings 44.windings 44 in opposition to the direct-current windings 42, the outputof the reactor 34 is so changed as to reduce the excitation of thesynchronous motor I0 and tend to force it to draw a lagging powerfactor.

In order to determine the power factor at which this forcing action ofthe direct-current windings 44 is limited and to provide a means forestablishing or selecting the power factor at which the system willregulate, another electric valve ||6 is disposed to control the bias ofthe grid 18 of the electric valve 12. The valve ||6 is similar to thevalve 12 having the same characteristics and being provided with ananode H8, a screen grid |20, a biasing grid |22, a heate- |24 and acathode |26.

As illustrated, the secondary windings 62 of transformer. are utilizedfor providing a negative bias on the grid |22, the windings 62 beingconnected across the input terminals of a rectifying bridge circuit |28,one of the output terminals of which is connected through the secondarywindings |30 of grid transformer |32 in the grid shift network system orphase shifting circuit |34 and resistor |36 to the grid |22, the otheroutput terminal of the bridge circuit |28 being connected by conductors|38 to the cathode |26.

The grid shift network |34 is supplied by the secondary windings 64 ofthe transformer 58, the secondary windings B4 being connected across theseries connected capacitor |40 and adjustable resistor |42, the primarywindings |44 of the grid transformer |32 being connected across themidpoint terminal of the secondary windings 64 and the junction of thecapacitor |40 and resistor |42. By adjusting the number of sections ofthe resistor |42 connected in the grid shift network system anadjustment is made in the phase angle in which the valve I6 becomesconducting, This adjustment is independent of the power factor of theload drawn by the synchronous motor I0.

The anode ||8 of the valve ||6 is connected by conductor |46 to aterminal of the secondary windings 66 of transformer 58, the otherterminal of the secondary windings 66 being connected by conductor |48through resistor |08 and conductors ||0, 94 and |50 to the cathode |26of valve H8. Thus the output of valve ||6 impresses a voltage on thegrid biasing circuit of valve 12 by reason of the interconnectedresistor |08 which is additive to the normal negative bias to definitelyrender the bias on grid 18 negative. This output is determined by thephase angle for which the grid shift network |34 is adjusted, such phaseangie being independent of the power factor of the load drawn by thesynchronous motor |0 as referred to hereinbefore.

Because of the characteristics of the valves 12 and H6, if valve 12 isrendered conductive by the action of the impulse transformer |02 inresponse to the power factor before valve ||6 is rendered conducting,the valve 12 will remain conductive for the remaining portion of thepositive half cycle of the voltage wave and the fir-- ing of the valve||6 will have no effect on the valve 12. However, if by reason of thephase angle adjustment of the network |34 or by reason of a change inthe power factor of the load system tending toward a lagging powerfactor, the impulse from the impulse transformer |02 should come laterin the voltage wave than the phase angle controlling the firing of valve||6 then the negative bias impressed on the grid circuit of valve 12 byreason of the valve ||6 being rendered conductive is sufiicient tomaintain the valve 12 non-conducting whereby the direct-current windingsi4 of the reactor 34 are maintained deenergized. Thus only thedirectcurrent windings 42 are active in so controlling 1 cathode |26of-valve ||6.

the saturation of the reactor 34 that the maximum permissible currentflows through the primary'windings of transformer 32 to affect themaximum permissibleexcitation of the synchronous motor I to cause it todraw a more leading power factor.

In operation, assuming that the resistors 5B and 56 have been adjustedto determine the excitation of the synchronous motor I0 for the maximumleading power factor which is to be permitted and that the resistor 88is adjusted to determine the maximum current flow through direct-currentwindings 44 for determining the iaggingpower factor of the motor l0, ifthen the switches 2li and 9a are actuated to their circuit closingpositions and the valves 12 and ||6 are heated for operation, thesynchronous motor I0 will draw a leading power factor.

Since the motor I0 draws a leading power factor, the impulse transfomer|02 functionsv to impress a peaked voltage on the grid-biasing circuitof valve 12 early in the positive half-cycle of the voltage wave torender the grid 18 less negative or more positive. When the ygrid 18 isbiased in this manner, the valve 12 will conduct current through thecircuit which extends from the anode 14 through conductor 82, switch 90,resistor 88, conductor 86, direct-current windings 44, conductor 84,secondary winding 68 of transformer 58 and conductors 94 and 96 to thecathode 82 of the valve 12. The direct-current flowing through thewindings 44 creates a flux in the core of reactor 34 which is inopposition to the flux resulting from the current flowing throughdirect-current windings to effect a reduction in the saturation ofreactor 34 and thereby lower the flow of alternating-current through theprimary windings of transformer 32. The resulting rectified currentflowing through the field windings 28 of the synchronous motor I0 isthus so reduced that the synchronous motor tends to draw amore laggingpower factor.

If the 'resistor |42 of the phase-shifting circuit |34 is adjusted todetermine the phase angle at which it is desired to limit the powerfactor of the synchronous motor I0, then as the excitation of the motorI0 isreduced to force the motor to tend to draw a lagging power factor,as soon as the phase`angle is reached that is established by thephase-shifting circuit |34, it is found that the valve ||6 becomesconducting ahead of valve 12. When the valve ||6 is conducting, currentflows. through the circuit extending from the anode ||8` throughconductor |46, `secondary winding 66 of transformer 58, conductor |48,re-

lthe valve "12 ahead of the negative bias impressed thereon by the valveIIS and the valve 12 thereby becomes conducting to again pass currentVto and through the direct-current windings 44 on the reactor 34. Theoutput of the reactor 34 is thus again reduced to so effect a reductioninthe excitation of the synchronous motor |0 that it tends sistor |08,and conductors ||0, 94 and |50 to the The flow of current through theresistor |08, which is interconnected in the output circuit of valve ||6and the gridbiasing circuit of valve 12, produces a potential vacrossthe part of resistor |08 in the grid-biasing circuit of valve 12 whichis additive to the negative bias of the rectifying bridge circuit 88 tomaintain the grid 18 negative regardless of the functioning thereafterof the impulse transformer |02 during that particular positive halfcycleof` the voltage wave.

When the valve 12 is thus rendered non-conductive, the current fiowing mthe direct-current windings 42 tends to saturate the reactor 34 andthereby effect an increase in the alternating-current flowing intheprimary windings of transformer 32. The resulting rectified currentowing through the field windings 26 of the synchronous motor |0 is thusso increased that to draw a more lagging power factor. It is thusevident that by adjusting 'resistor |42 of the 'phase-shift circuit |34,it is possible to select any predetermined power factor at which it isdesired to have the synchronous motor |0 operate.

Although an anti-hunting circuit is not illustrated, it is apparent thatany suitable circuit which imposes a potential on the grid biasingcircuit of valve 12, such potential varying as the excitation of thesynchronous motor |0 varies, may be utilized for controlling the bias ofthe valve 12 in anticipation of the change in excitation of thesynchronous motor |0 to prevent an Vexcessive overrun in the change inthe excitation of the motor. Such anti-hunting circuits are well knownand can be successfully incorporated in the system herein described.

The system described as embodying the teachings of this invention iscomposed of standard components such as require very little care andattention. Once the phase angle is determined at which it is desired toregulate and thephaseshifting circuit |34 is adjusted for such phaseangle, the system requires no further maintenance. It will, of course,be understood that where it is desired to regulate for a different powerfactor that such regulation can lbe readily obtained by adjusting thephase-shift circuit to so control the saturation of the reactor as tomaintain the excitation ofthe synchronous motor that it draws theselected power factor. Further, with the system of this invention thereis no limit as to the size of the synchronous motor which is to becontrolled as the reactor and cooperating rectifying bridge circuits canbe made in accordance with the conditions which are to be encountered.

Although this invention has been described with reference to aparticular embodiment thereof, it is, of course, not to be limitedthereto except insofar as is necessitated by the scope of the appendedclaims. 1

I claim as my invention:

1. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor'- having opposed direct-current control windings, oneof the wind- 'ings being disposed to be energized to effectsaturation'of the reactor to increase the excitation of the motor, theother of the windings functioning when energized to effect a decrease inthe saturation of the reactor, means responsive to the power factor ofthe load system disposed to control the energization of the otherwinding, and means responsive to a fixed phase angle disposed to preventthe operation of the power factor responsive means to 'prevent theenergization of the other winding under predetermined power factorconditions whereby the excitation of the synchronous motor is maintainedwithin predeterfiiined limits to regulate the power factor thereof.

2. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor having opposed direct-current control windings, oneofthe Windings being disposed to be energized to effect saturation ofthe reactor to increase the excitation of the motor, the other of thewindings functioning when energized to effect a decrease in thesaturation of the reactor, means responsive to the power factor of theload system disposed to control the energization of the other winding,and electric valve means responsive to a fixed phase angle disposed toprevent the operation of the power factor responsive means to preventthe energization of the other winding under predetermined power factorconditions whereby the excitation of the synchronous motor is maintainedwithin predetermined limits to regulate the power factor thereof.

3. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor having opposed direct-current contro-i windings, oneof the windings being disposed to be energized to effect saturation ofthe reactor to increase the excitation of the motor, the other of thewindings functioning when energized to effect a decrease in thesaturation of the reactor, means including an electric valve disposed toconnect the other winding to a source of power, the electric valvehaving a grid to be utilized for controlling the conductivity thereof, agrid circuit responsive to the power factor of the load system forcontrolling the bias of the grid to control .the energization of theother winding, and means cooperating in the grid circuit of the electricvalve to maintain the valve non-conducting under predetermined powerfactor conditions.

4. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor having opposed direct-current'control windings, one ofthe windings being disposed to be energized to effect saturation of thereactor-'to increase the excitation of the motor, the other of thewindings functioning when energized to effect a decrease in thesaturation of the reactor, means including an electric valve disposed toconnect the other winding to a source of power, the electric valvehaving a grid to ce utilized for controlling the conductivity thereof, agrid circuit responsive to the power factor of the load system forcontrolling the bias of the grid to control the energizetion of theother winding, and means responsive to a predetermined phase angledisposed to cooperate in the grid circuit of the electric valve tomaintain the valve non-conducting under predetermined power factorconditions.

5. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor having opposed direct-current control windings, one ofthe windings being disposed to be energized to effect saturation of thereactor to increase the excitation of the motor, the other of thewindings functioning when energized to effect a decrease in thesaturation of the reactor, means including an electric valve disposed toconnect the other winding to a source of power, the electric valvehaving a grid to be utilized for controlling the conductivity thereof,means for applying a negative bias to the grid, means for rendering thegrid positive in response to the phase angle of the system to controlthe energization of the other winding, the positive biasing meansincluding an impulse transformer connected to be responsive to the flowof current in the load system, and means responsive to a predeterminedphase angle disposed to cooperate in the grid circuit of the electricvalve to maintain the valve non-conducting under predetermined powerfactor conditions.

6. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor machine having opposed direct-current controlwindings, one of the windings being disposed to be energized to effectsaturation of the reactor to increase the excitation of the motor, theother of the windings functioning when energized to effect a decrease inthe saturation of the reactor, a plurality of electric valves havinggrids for controlling the energization of the other winding, one of thevalves being disposed to connect the other winding to a source of power,a grid circuit responsive to the power factor of the load system forcontrolling the bias of the grid of the one valve to render the onevalve conducting, the other valve being connected to impress a negativebias on the grid of the one valve to render it non-conducting when theother valve is rendered conducting ahead of the one valve, the othervalve having a grid biasing circuit responsive to a predetermined phaseangle whereby the other valve cooperates with the grid biasing circuitof the one valve to maintain the one valve non-conducting underpredetermined power factor conditions of the load system.

7. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor having opposed windings, one of the windings beingdisposed to be energizedto effect saturation of the reactor to increasethe excitation of the motor, the other of the windings functioning whenenergized to effect a decrease in the saturation of the reactor, aplurality of electric valves having grids for controlling theenergization of the other winding, one of the valves being disposed toconnect the other winding to a.` source of power, a grid circuitresponsive to the power factor of the load system for controlling thebias of the grid of the one valve to render the one valve conducting,the other valve having a grid biasing circuit responsive to apredetermined phase angle to render the other valve conducting, andmeans interconnecting the output of the other valve with the gridbiasing circuit of the one valve whereby the other valve impresses anegative bias on the grid of the one valve to render it non-conductingwhen the other valve is rendered conducting ahead of the one valve.

8. In a system for regulating the power factor of a synchronous motorconnected to a load system, in combination, a saturable reactorconnected to control the excitation of the synchronous motor, thesaturable reactor having opposed direct-current control windings, one ofthe wind- A 9 ings being disposed to be energized to eifect satura'tionof the reactor to increase the excitation of the motor, the other of thewindings functioning when energized to effect a decrease in the minedphase angle to render the other valve con.

l0 ducting, and means interconnecting the output of the other valve withthe grid biasing circuit of the one valve whereby the other valveimpresses a negative bias on the grid of the one valve to render itnon-conducting when the other valve is rendered conducting ahead of theone valve.

HAROLD C. JENKS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date West Apr. 30, 1929 Nmber

